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Vitamin D can help with blood sugar levels and insulin production, so some research indicates it can help people with prediabetes avoid a diagnosis of type 2 diabetes. Getty Images

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  • A new study concludes that people with prediabetes who take vitamin D supplements can lower their risk of type 2 diabetes.
  • Past research indicates that vitamin D can positively affect blood sugar levels, inflammation, and insulin production.
  • It can be difficult to obtain enough vitamin D through your diet, so sunshine and supplements can be options.

People with prediabetes who supplement with at least 1,000 units per day of vitamin D may significantly reduce their risk of progressing to a diagnosis of type 2 diabetes.

That’s the conclusion of recent research published in The Journal of Clinical Endocrinology & Metabolism.

The meta-analysis included nearly 45,000 participants from nine previous clinical trials. Those participating had an average age of 65 years.

With the large sample size, the researchers said they were striving to determine more clearly if a deficiency in vitamin D increases the risk of type 2 diabetes and if supplements taken by people with prediabetes could prevent further progression of the disease.

Past research has determined that about 41 percent of the U.S. population has lower than normal vitamin D levels.

When focusing on specific ethnicities, nearly 82 percent of African American adults and 62 percent of Hispanic adults were found to be deficient in vitamin D. The factors for those percentages included obesity, lack of college education, and lack of daily milk consumption.

Dr. Zachary Bloomgarden, a professor at Mount Sinai Hospital in New York City specializing in endocrine and diabetes care, says the association between vitamin D and type 2 diabetes has been studied many times.

“The random controlled trials have not convincingly showed that vitamin D prevents diabetes, but subset analogies suggest that the group of individuals with low vitamin D levels are protected from diabetes by taking a vitamin D supplement,” Bloomgarden told Healthline.

A 2017 study posed theories that vitamin D affects blood sugar levels and reduces the risk of type 2 diabetes in three ways: insulin production, insulin sensitivity, and overall inflammation.

And this doesn’t just apply to adults.

In a study focused on Swedish youth who have obesity, vitamin D deficiency and prediabetes were identified in 33 percent of the participants.

“Vitamin D is really a prohormone,” explained Bloomgarden. “Chemically, it’s a steroid hormone.”

The fact that insulin is also a hormone convinces some experts that there is a relationship between insulin and vitamin D. Many people with low vitamin D levels have also been found to have overall immune deficiencies.

Bloomgarden adds, however, that while vitamin D deficiency is common in people with obesity and type 2 diabetes, it’s difficult to say what causes what.

Vitamin D is a fat-soluble vitamin, which means it can be stored in fat cells like vitamins A, E, and K.

The storage factor means a person can consume too much of any fat-soluble vitamin and experience negative effects.

Other vitamins are water-soluble, which means that consuming too much will prompt the body to excrete the excess material through the urine.

Unlike most other vitamins, it’s difficult to obtain vitamin D from your diet. Instead, sunlight exposure triggers the synthesis of vitamin D in the human body.

“Vitamin D deficiency is common in the general population, but mild degrees of vitamin D deficiency is not associated with any noticeable symptoms or issues,” explained Bloomgarden.

At his practice, Bloomgarden says he measures vitamin D levels in all patients. Anyone with a deficiency is treated with a supplement.

He says that in people with obesity, vitamin D deficiency is significant and common.

Bloomgarden classifies his patients’ vitamin D levels as the following:

  • Normal: 30 nanograms per milliliter (ng/mL)
  • Mild deficiency: 20 to 30 ng/mL
  • Moderate deficiency: 10 to 20 ng/mL
  • Severe deficiency: below 10 ng/mL

“I don’t always treat someone with a mild deficiency,” explained Bloomgarden, adding there doesn’t seem to be any noticeable benefit for those people.

Bloomgarden recommends the following replacement doses based on your vitamin D levels:

  • 25 ng/mL and above: 1,000 units per day
  • 20 to 25 ng/mL: 2,000 units per day
  • 15 to 20 ng/mL: 2,000 units per day
  • 10 to 15 ng/mL: 3,000 units per day
  • Below 10 ng/mL: 4,000 units per day for 1 month, then reduce

Bloomgarden said that older theories on vitamin D replacement and supplementation recommended only 400 units per day, but newer research shows that isn’t enough.

“I’d only measure a patient’s levels again if they were severely low in the initial testing,” explained Bloomgarden. “After a month or several months of supplementation, I’d measure again. I’d also measure calcium levels to ensure we’re not overdosing vitamin D.”

Taking too much vitamin D can significantly increase the amount of calcium you absorb from the foods you eat. While this may sound like a good thing, it can become dangerous at high enough levels.

“Elevated blood calcium leads to a number of issues, including kidney stones,” said Bloomgarden.

There have been recommendations of up to 10,000 units per day, which Bloomgarden feels isn’t necessary or safe.

“One thousand units per day for most people is plenty,” said Bloomgarden. “Very few people need more than that.”

Ginger Vieira has lived with type 1 diabetes and celiac disease since 1999 and fibromyalgia since 2014. She’s the author of four books: “Pregnancy with Type 1 Diabetes,” “Dealing with Diabetes Burnout,” “Emotional Eating with Diabetes,” and “Your Diabetes Science Experiment.” Ginger creates content regularly for Diabetes Strong, Diathrive, YouTube, and Instagram. Her background includes a bachelor of science degree in professional writing and certifications in coaching, personal training, and yoga.